1. Field of the Invention
This invention relates to endotracheal tubes, and more specifically to endotracheal tubes having a portion with an angular cross section.
2. Related Art
Endotracheal tubes have been used extensively in medical applications for ventilating a patient, for example during surgery, after lung failure, and for suction. Endotracheal tubes are round in cross section, both internally and externally, and are generally suitable for short surgeries. However, during long surgery or prolonged ventilation, contact between the round external surface of the endotracheal tube causes irritations in the vocal cords in the area where the tube makes contact. The irritation produces erosion of the vocal cord area where the prolonged contact occurs.
Irritation to the vocal cords is produced when the rounded surface of present endotracheal tubes makes prolonged contact with the vocal cords. Because the vocal cords have two parts which are angled with respect to each other, the inside surfaces of the vocal cords converge, when viewed in a transverse cross section, to a point. Each side of the vocal cords is relatively straight so that when the round tube contacts the vocal cords, for example due to bending or movement of the tube, it is believed that the entire force of any tube contact with the vocal cords is concentrated at the points on the vocal cords tangent to the rounded surface of the tube. This localizes the contact between the tube and the vocal cords, thereby ultimately producing irritation and inflamation.
There is a need, therefore, for an endotracheal tube which minimizes the possibility of contact between the tube and the vocal cords, and in the case of any such contact, distributes the force of the contact over a wide area. The endotracheal tube should still be flexible to allow the tube to be passed along the trachea and below the vocal cords. The present invention provides such an endotracheal tube.